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The Max Controllers

There are several iterations of the Max design, they all aim for roughly the same feature set:

  • Control of four stepper motors using StepStick drivers.  This provides two motors for the mount, a rotator, and a focuser (or two focusers.)
  • External connectors for power in, illuminated reticle, stepper motors, limit sense, PEC, home switches, encoders, ST4, and USB.
  • Internal connectors for an RTC (DS3231) and WeMos D1 Mini footprint (WiFi or Ethernet can plug in.)
  • Designed for a readily available aluminum project box.

The designs, in order, with the most recent (and most refined) first:

  • MaxSTM3.6
    • Uses the STM32F401 or STM32F411 processor.  Moderately fast, similar to ESP32 speeds.
    • Has the most external I/O connections of any Max series controller.
    • Works only with SPI StepStick TMC2130 or TMC5160 drivers in all axes.
    • Allows driver setup (microstep mode, current, etc.) at runtime for all axes.
    • There is also a, basically identical in function, SMT version: MaxSTM3.6 (SMT).
    • Also, this has the most refined assembly instructions.
  • MaxESP3
    • Uses the ESP32 processor, moderately fast.
    • Intended for SPI StepStick TMC2130 or TMC5160 drivers in Axis1/2 (mount.)
    • Allows driver setup (microstep mode, current, etc.) at runtime for Axis1/2 only.
    • Uses only traditional StepStick drivers in Axis3/4 (focuser and rotator.)
    • Has the least I/O connections of any Max, which can be limiting.
  • MaxPCB2
    • Uses the Teensy3.5 or Teensy3.6 processor.  Faster than ESP32 speeds.
    • Works with most StepStick drivers, TMC2130, TMC5160, and others in Axis1/2 (mount.)
    • Allows driver setup (microstep mode, current, etc.) at runtime for Axis1/2 only.
    • Uses only traditional StepStick drivers in Axis3/4 (focuser and rotator.)

Why several generations?

  • The first and second generation uses Teensy processors, they are nice (excellent quality, performance, and software libraries) but they are expensive and availability world-wide is limited.
  • The ESP32 brings down the cost and is widely available but the lack of pins lead to compromises in the design.  The ESP32's ability to do WiFi and Bluetooth (onboard) is nice but this design has a coprocessor (usually an ESP8266) that provides WiFi and additional I/O for encoders anyway making the ESP32 WiFi and Bluetooth largely redundant.
  • The STM32 F411 "Blackpill" entered the market later and now has low cost and good availability as well AND it has more pins so it represents the best overall choice presently.

If you are looking for information on an even earlier version (obsolete) of the Max series that page can be found here.